The proposed studies focus on establishing an objective, standardized, and high-throughput method for quantifying open field exploratory behavior in the mouse. Conventional assessment of general activity derived from open field studies will be extended to include new, ethologically relevant measures that will be computed from automatically measured time-series of animal location. These measures will define behavioral patterns that comprise the temporal and spatial structure of mouse exploratory behavior and identify which patterns have the highest potential as a phenotyping tool. The discrimination power of these measures will be tested on 17 of the most used inbred mouse strains. A database of mouse exploratory behavior will be established as well as a standard protocol. The protocol, database, and user-friendly software that will include already tested algorithms, will be made available to researchers in the field on a freely accessible website.